Piezoelectric Element

This application is national stage application of International Application No. PCT/JP 2023/036764, filed on Oct. 10, 2023, which designates the United States, incorporated herein by reference, and which claims the benefit of priority from Japanese Patent Application No. 2022-165512, filed on Oct. 10, 2022, the entire contents of which are incorporated herein by reference.

The disclosed embodiments relate to a piezoelectric element.

A known piezoelectric element includes a laminate body with a plurality of piezoelectric bodies and a plurality of internal electrodes laminated, an electrical conductor layer located on the side surface of the laminate body and connected to the internal electrodes, and an electrode plate part of which in a width direction is bonded to the electrical conductor layer via an electrically conductive bonding material (see, for example, Patent Document 1). In a proposed structure of the piezoelectric element, the electrical conductor layer and the electrode plate are covered with a coating layer located on the side surface of the laminate body (see, for example, Patent Document 2).

Patent Document 1: JP 2008-211054 A

Patent Document 2: JP 2006-41279 A

A piezoelectric element according to one aspect of an embodiment includes a laminate body, an electrical conductor layer, an electrode plate, and a coating layer. The laminate body includes a plurality of piezoelectric bodies and a plurality of internal electrodes laminated. The electrical conductor layer is connected to the internal electrodes and is positioned along the laminate direction of the laminate body. The electrode plate is bonded to the electrical conductor layer via an electrically conductive bonding material and is positioned along the laminate direction of the laminate body. The coating layer covers the electrical conductor layer and the electrode plate. The electrode plate includes a plurality of slits extending in a direction intersecting the laminate direction. The piezoelectric element includes a first gap between the electrode plate, the electrical conductor layer, and the bonding material.

One aspect of the embodiment allows the possibility of separation of the electrode plate covered with the coating layer to be reduced.

An embodiment of a piezoelectric element disclosed in the present application will be described below with reference to the attached drawings. Note that the present disclosure is not limited by the following embodiment. It is noted that the drawings are schematic, and the relationship between the dimensions of each element and the ratio of each element may differ from the reality. Furthermore, even between the drawings, portions may be included having the relationship between the dimensions of each element, and the ratio of each element, differ.

1 1 1 FIG. 1 FIG. An overall configuration of a piezoelectric elementaccording to the embodiment will be described with reference to.is a perspective view illustrating an overall configuration of the piezoelectric elementaccording to the embodiment.

1 FIG. 3 4 FIGS.and 1 FIG. 1 10 20 40 50 20 20 20 40 40 40 50 20 40 As illustrated in, the piezoelectric elementaccording to the embodiment includes a laminate body, a pair of electrical conductor layers, a pair of electrode plates, and a coating layer(see). The pair of electrical conductor layersincludes an electrical conductor layerA and an electrical conductor layerB, and the pair of electrode platesincludes an electrode plateA and an electrode plateB. In, the illustration of the coating layer, the electrical conductor layerB, and the electrode plateB is omitted for convenience of description.

10 10 10 The laminate bodyhas a pillar shape. The laminate bodyhas, for example, a quadrangular prism shape (rectangular parallelepiped shape) with a length of 0.5 mm to 10 mm, a width of 0.5 mm to 10 mm, and a height of 1 mm to 100 mm. Note that the shape of the laminate bodyis not limited to a quadrangular prism but may be a hexagonal prism, an octagonal prism, or a cylinder.

10 11 12 13 10 11 12 13 10 10 The laminate bodyincludes a plurality of piezoelectric bodies, a plurality of internal electrodes, and a plurality of planned breaking layers. The laminate bodyis composed by laminating the plurality of piezoelectric bodies, the plurality of internal electrodes, and the plurality of planned breaking layersin a predetermined order along the laminate direction D. In the present disclosure, the laminate direction D of the laminate bodycoincides with the longitudinal direction of the laminate body.

11 3 3 3 3 A piezoelectric bodyis made of a piezoelectric material having piezoelectric properties, for example, piezoelectric ceramics. The material of the piezoelectric ceramics is, for example, a perovskite oxide composed of lead zirconate titanate (PbZrO—PbTiO), a lithium niobate (LiNbO), or a lithium tantalate (LiTaO).

11 The average particle diameter of the piezoelectric ceramics is, for example, 1.6 μm to 2.8 μm. The thickness of the piezoelectric bodyis, for example, 3 μm to 250 μm.

12 12 12 12 20 10 10 12 20 a b a a a The internal electrodesare made of an electrically conductive material and include a plurality of first electrodesand a plurality of second electrodes. The first electrodeis electrically connected to the electrical conductor layerA arranged on one side surfaceof the laminate body. A predetermined positive voltage is applied to the first electrodevia the electrical conductor layerA.

12 20 10 10 10 12 20 b b a b The second electrodeis electrically connected to an electrical conductor layerB arranged on the side surfaceopposite to the side surfaceof the laminate body. A predetermined negative voltage (or ground voltage) is applied to the second electrodevia the electrical conductor layerB.

10 12 12 11 11 12 12 10 11 12 12 a b a b a b. Inside the laminate body, the first electrode, the second electrodeand the piezoelectric bodyare stacked such that the piezoelectric bodyis arranged between the first electrodeand the second electrode. This allows the laminate bodyto apply a drive voltage to the piezoelectric bodyby the first electrodeand the second electrode

10 11 12 11 The laminate bodyaccording to the embodiment is composed of an active section composed by alternately laminating the plurality of piezoelectric bodiesand the plurality of internal electrodesand an inactive section that is arranged at both ends in the laminate direction D in the active section and includes the piezoelectric bodies.

10 10 The active section is a site that extends or contracts (hereinafter also referred to as stretch) in the laminate direction D when a drive voltage is applied to the laminate bodyfrom the outside. On the other hand, the inactive section is a site that does not stretch even when a drive voltage is applied to the laminate bodyfrom the outside.

1 FIG. 1 FIG. 10 10 10 10 e f In the present disclosure, the lower end portion ofis a base end portionof the laminate body, and the upper end portion ofis a front end portionof the laminate body.

1 10 10 10 10 e f In the piezoelectric elementaccording to the embodiment, the base end portionof the laminate bodyis fixed, and the front end portionof the laminate bodyis displaced along the laminate direction D.

12 12 11 12 The material of the internal electrodeis, for example, a metal mainly composed of silver, silver-palladium, silver-platinum, or copper. The internal electrodecan be formed by, for example, co-firing with the piezoelectric body. The thickness of the internal electrodeis, for example, 0.1 μm to 5 μm.

13 10 13 12 10 13 The planned breaking layeris a layer for relieving stress caused by driving the laminate body. Examples of the planned breaking layerinclude a porous metal layer that does not function as the internal electrodeor a metal layer with a crack in advance. In the laminate bodyaccording to the embodiment, the planned breaking layermay be omitted.

20 20 10 10 20 10 10 20 10 20 a b As described above, the pair of electrical conductor layersincludes the electrical conductor layerA located on the side surfaceof the laminate bodyand an electrical conductor layerB located on the side surfaceof the laminate body. The electrical conductor layeris arranged over the entire active section of the laminate body. The electrical conductor layeris located along the laminate direction D.

20 20 20 The material of the electrical conductor layeris, for example, a metal composed mainly of silver or copper. For the electrical conductor layer, for example, a metallization layer made of the sintered body of the metal and glass can be used. The thickness of the electrical conductor layeris, for example, 5 μm to 500 μm.

40 40 40 20 40 20 40 20 The pair of electrode platesincludes the electrode plateA and the electrode plateB and is electrically connected to the pair of electrical conductor layerson a one-to-one basis. Specifically, the electrode plateA is electrically connected to the electrical conductor layerA, and the electrode plateB is electrically connected to the electrical conductor layerB.

40 10 40 20 30 30 The electrode plateis located along the laminate direction D of the laminate body. A part of the electrode platein the width direction intersecting the laminate direction D is bonded to the electrical conductor layervia an electrically conductive bonding material. The bonding materialis, for example, epoxy resin or polyimide resin containing metal powder having high electrical conductivity, such as Ag powder or Cu powder.

40 40 40 40 The material of the electrode plateis, for example, a metal such as copper, iron, stainless steel, phosphor bronze. The width of the electrode plateis, for example, 0.5 mm to 10 mm, and the thickness of the electrode plateis, for example, 0.01 mm to 1.0 mm. To improve electrical and thermal conductivity, the surface of the electrode platemay be coated with a plating film such as tin plating or silver plating.

50 10 10 10 20 40 50 10 10 a b a b The coating layeris positioned on the entire circumference of the side surfaces including the side surfacesandof the laminate bodyand covers the electrical conductor layerand the electrode plate. Arranging the coating layeron the side surfacesandallows surface discharge between both the electrodes that occurs in applying high voltage during driving to be reduced.

50 50 The coating layeris made of, for example, an insulator. For example, fluorine-based resin, silicone resin, epoxy resin, nylon resin, or the like are used as the insulator to be the coating layer.

50 10 10 10 20 40 50 10 10 10 10 10 a b c d a b. The coating layeris positioned at least on the side surfacesandof the laminate bodyso as to cover the electrical conductor layerand the electrode plateand is not necessarily be located on the entire circumference of the side surfaces. For example, the coating layermay not be positioned on side surfacesandof the laminate bodybut may be located only on the side surfacesand

40 50 40 50 2 4 FIGS.to 2 FIG. 3 FIG. 2 FIG. 4 FIG. 2 FIG. 2 FIG. The detailed configuration of the electrode plateand the coating layeraccording to the embodiment will be described with reference to.is an enlarged plan view illustrating an example of the configuration of the electrode plateand its surroundings according to the embodiment.is a cross-sectional view taken along line III-III in.is a sectional view taken along line IV-IV in. In, the illustration of the coating layeris omitted for convenience of description.

40 10 40 20 30 As described above, the electrode plateis a plate-like member extending in the laminate direction D of the laminate body, and a part of the electrode platein the width direction intersecting the laminate direction D is bonded to the electrical conductor layervia an electrically conductive bonding material.

2 FIG. 40 40 As illustrated in, in the embodiment, the electrode plateincludes a plurality of slits S. The slits S are cut so as to extend along the width direction (i.e., the direction intersecting the laminate direction D) of the electrode plate, for example.

40 30 40 40 The slits S are cut alternately from the end surfaces of both end portions of the electrode platepositioned outside from the bonding materialin the width direction of the electrode platein a plan view and are arranged at substantially equal intervals along the laminate direction D. The plurality of slits S have substantially equal lengths. Note that the length of the slit S is the length in the notch direction of the slit S (i.e., the width direction of the electrode plate).

Furthermore, each length of the plurality of slits S is set so that the front end overlaps each other when viewed in the laminate direction D. “Overlap” means that the adjacent slits S have areas facing each other when viewed in the laminate direction D.

40 40 10 40 10 20 In the embodiment, arranging the plurality of slits S in the electrode plateenables the electrode plateto stretch in the laminate direction D following the stretch of the laminate bodyin the laminate direction D. Therefore, the embodiment can reduce the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

40 20 50 10 3 4 FIGS.and On the other hand, the electrode plateis covered together with the electrical conductor layerby the coating layer(see) located on the side surfaces of the laminate body.

40 20 50 10 40 40 40 30 40 40 10 40 10 20 If the periphery of the electrode plateand the electrical conductor layeris completely covered with the coating layer, when the laminate bodystretches, a large stress that restricts the deformation of the electrode plateis generated in the electrode plate. In particular, the stress that restricts the deformation of the twist is concentrated on the end portion of the electrode platepositioned outside from the bonding materialin the width direction of the electrode platein a plan view. The stress that restricts the deformation is generated in the electrode platefollowing the stretching of the laminate body, and the electrode platemay thus separate from the laminate bodyor the electrical conductor layer.

3 4 FIGS.and 2 FIG. 20 40 50 30 40 20 1 40 20 30 40 30 40 20 As illustrated in, in the embodiment, the electrical conductor layerand the electrode plateare covered with the coating layerwith a gap G left between the end portions located outside the bonding materialin the width direction of the electrode platein a plan view and the electrical conductor layer. In other words, in the embodiment, the piezoelectric elementincludes the gap G among the electrode plate, the electrical conductor layer, and the bonding material. A plurality of such gaps G are formed at positions that do not overlap the plurality of slits S of the electrode platein a plan view (see). The end portions positioned outside from the bonding materialin the width direction of the electrode platein a plan view is located facing the electrical conductor layeracross the gap G. The gap G is an example of a first gap.

20 40 50 40 10 40 40 10 40 10 20 In the embodiment, covering the electrical conductor layerand the electrode platewith the coating layerwith the gap G left causes deformation of the twist to occur at the end portions of the electrode platein the width direction following the stretch of the laminate bodyin the laminate direction D, allowing the electrode plateto be easily deformed. Thus, the embodiment can relax the stress generated in the electrode platedue to the stretch of the laminate body, thereby reducing the possibility of separation of the electrode platefrom the laminate bodyor the electrical conductor layer.

2 3 FIGS.and 40 30 40 20 40 20 40 20 40 20 30 40 40 10 40 10 40 10 20 In the embodiment, as illustrated in, a gap G between one end portion of the electrode platepositioned outside from the bonding materialin a width direction of the electrode platein a plan view and the electrical conductor layeris separated from a gap G between the other end portion of the electrode plateand the electrical conductor layer. That is, the one gap G between one end portion of the electrode plateand the electrical conductor layer, and the other gap G between the other end portion of the electrode plateand the electrical conductor layer, are not connected and are closed individually with the bonding materialas a boundary. Separating the gap G at the one end portion and the gap G at the other end portion of the electrode plateenables twist deformation to more easily occur at both ends of the electrode platein the width direction following the stretch of the laminate bodyin the laminate direction D. Therefore, the embodiment can further relax the stress generated in the electrode platedue to the stretch of the laminate body, thereby reducing the possibility of separation of the electrode platefrom the laminate bodyor the electrical conductor layer.

2 FIG. 40 20 40 20 10 40 10 40 10 40 10 20 In the embodiment, as illustrated in, one gap G between one end portion of the electrode plateand the electrical conductor layer, and the other gap G between the other end portion of the electrode plateand the electrical conductor layer, are disposed at positions that are mutually displaced in the laminate direction D of the laminate body. This enables the twist deformation to be more easily generated at both ends of the electrode platein the width direction, following the stretch of the laminate bodyin the laminate direction D. Therefore, the embodiment can further relax the stress generated in the electrode platedue to the stretch of the laminate body, thereby reducing the possibility of separation of the electrode platefrom the laminate bodyor the electrical conductor layer.

2 FIG. 30 40 40 30 40 10 40 10 40 40 10 20 In the embodiment, as illustrated in, the bonding materialmay be positioned overlapping the center portion of the electrode platein a plan view. This results in that the gap G on one end side and the gap G on the other end side of the electrode platedivided via the bonding materialcan be substantially the same size. Thus, the twist deformation occurs equally at both ends of the electrode platein the width direction, following the stretch of the laminate bodyin the laminate direction D. Accordingly, the embodiment allows the stress generated in the electrode platedue to the stretch of the laminate bodyto be equally relaxed at both ends of the electrode platein the width direction, thereby reducing the possibility of separation of the electrode platefrom the laminate bodyor the electrical conductor layer.

2 FIG. 30 40 40 30 40 In the embodiment, as illustrated in, the bonding materialmay have a region overlapping the slit S of the electrode platein a plan view. This allows the electrode plateto be difficult to separate from the bonding materialnear the slit S of the electrode plate.

40 40 40 30 40 40 30 In the embodiment, the length of the slit S of the electrode plateis larger than half the width of the electrode plate. This causes the position of the front end in the direction of the notch of the slit S, which is the origin of the twist generated at the end portion of the electrode platein the width direction, to be offset from the position of the bonding materiallocated at the center of the electrode plate. Thus, the electrode plateis difficult to separate from the bonding material.

5 23 FIGS.to Other various embodiments will be described with reference to. Note that in the following other various embodiments, portions that are the same as those in the embodiments will be denoted by the same reference signs, and redundant explanations may be omitted.

5 6 FIGS.and 5 FIG. 2 FIG. 6 FIG. 2 FIG. 40 are cross-sectional views illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment 1.corresponds to a cross-sectional view taken along line III-III illustrated in, andcorresponds to a cross-sectional view taken along line IV-IV illustrated in.

5 6 FIGS.and 5 FIG. 50 50 51 51 40 20 40 51 In the other embodiment 1 illustrated in, the configuration of the coating layeris different from the above embodiment. Specifically, in the other embodiment 1, as illustrated in, the coating layerincludes a protruding portion. The protruding portionprotrudes inward from the end portion of the electrode platein the direction intersecting the laminate direction D (i.e., the width direction) and contacts the electrical conductor layer. Here, “inward” means the side toward the center of the electrode plate. The protruding portionis an example of a first protruding portion.

51 50 50 20 51 40 50 20 40 50 20 In the other embodiment 1, by providing the protruding portionin the coating layer, the adhesion force between the coating layerand the electrical conductor layeris improved compared with the case with the protruding portionnot provided. Therefore, the adhesion force between the electrode platecovered with the coating layerand the electrical conductor layeris improved. Therefore, the other embodiment 1 can reduce the possibility that the electrode platecovered with the coating layerseparates from the electrical conductor layer.

6 FIG. 50 52 52 40 20 52 In the other embodiment 1, as illustrated in, the coating layermay include a protruding portion. The protruding portionis positioned so as to project more inward than the inner wall surface of the slit S in the electrode plateand contacts the electrical conductor layer. Here, “inward” means the side approaching the center of each electrode plate. The protruding portionis an example of a second protruding portion.

52 50 50 20 52 40 50 20 40 50 20 By providing the protruding portionin the coating layer, the adhesion force between the coating layerand the electrical conductor layeris improved compared with when the protruding portionis not provided, so that the adhesion force between the electrode platecovered with the coating layerand the electrical conductor layeris improved. Therefore, the other embodiment 1 can reduce the possibility that the electrode platecovered with the coating layerseparates from the electrical conductor layer.

7 8 FIGS.and 7 FIG. 2 FIG. 8 FIG. 2 FIG. 40 are cross-sectional views illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment 2.corresponds to a cross-sectional view taken along line III-III illustrated in, andcorresponds to a cross-sectional view taken along line IV-IV illustrated in.

7 8 FIGS.and 7 FIG. 40 40 41 40 40 41 In the other embodiment 2 illustrated in, the configuration of the electrode plateis different from that of the other embodiment described above. Specifically, in the other embodiment 2, as illustrated in, the electrode plateincludes a projecting portionprojecting in the thickness direction of the electrode plateat the periphery of the end portion of the electrode platein the direction crossing the laminate direction D (i.e., the width direction). The projecting portionis an example of a first projecting portion.

41 40 40 41 40 40 41 10 10 10 7 FIG. In the other embodiment 2, by providing the projecting portionin the electrode plate, the strength of both end portions at the electrode plateis increased compared with when the projecting portionis not provided, so that damage to both ends of the electrode platecaused by repeated deformation is less likely to occur. Therefore, the other embodiment 2 enables the durability of the electrode plateto be improved. In, the projecting portionis positioned on each of the side of the laminate bodyand on the opposite side of the laminate bodybut may be positioned only on the side of the laminate body.

51 50 41 41 40 10 40 10 40 10 20 In the other embodiment 2, the thickness of the protruding portionof the coating layerlocated near the projecting portionis reduced by the thickness of the projecting portion, so that the electrode platecan be easily deformed, following the stretch of the laminate bodyin the laminate direction D. Therefore, the other embodiment 2 can further relax the stress generated in the electrode platedue to the stretch of the laminate body, thereby reducing the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

41 10 40 40 40 In the other embodiment 2, the projecting portionmay extend along the laminate direction D of the laminate body. As a result, the strength of both end portions of the electrode plateis increased, so that damage to both end portions of the electrode platecaused by repeated deformation is less likely to occur. Therefore, the other embodiment 2 allows the durability of the electrode plateto be further improved.

8 FIG. 40 42 40 40 42 In the other embodiment 2, as illustrated in, the electrode platemay include a projecting portionprojecting in the thickness direction of the electrode plateat the periphery of the slit S in the electrode plate. The projecting portionis an example of the second projecting portion.

42 40 40 42 40 40 42 10 10 10 8 FIG. By providing the projecting portionin the electrode plate, the strength of the periphery of the slit S in the electrode plateincreases compared with when the projecting portionis not provided, and thus, the damage of the periphery of the slit S in the electrode platedue to repeated deformation is less likely to occur. Therefore, the other embodiment 2 enables the durability of the electrode plateto be improved. In, the projecting portionis positioned on each of the side of the laminate bodyand on the opposite side of the laminate bodybut may be positioned only on the side of the laminate body.

52 50 42 42 40 10 40 10 40 10 20 In the other embodiment 2, the thickness of the protruding portionof the coating layerlocated near the projecting portionis reduced by the thickness of the projecting portion, so that the electrode platecan be easily deformed, following the stretch of the laminate bodyin the laminate direction D. Therefore, the other embodiment 2 can further relax the stress generated in the electrode platedue to the stretch of the laminate body, thereby reducing the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

42 40 40 40 In the other embodiment 2, the projecting portionmay extend along the longitudinal direction of the slit S. As a result, the strength of the periphery of the slit S in the electrode plateincreased, so that the damage of the periphery of the slit S in the electrode platecaused by repeated deformation is less likely to occur. Therefore, the other embodiment 2 allows the durability of the electrode plateto be further improved.

41 42 40 40 a 7 FIG. The formation of the projecting portionsandcan be achieved by etching the side surface of a metal plate(see), which is the base material of the electrode plate, to form a concave portion and then plating the corner portion located at the periphery of the concave portion thicker than other portions.

9 FIG. 9 FIG. 40 40 40 is an enlarged plan view illustrating an example of the configuration of the electrode plateaccording to the other embodiment 3. In the other embodiment 3 illustrated in, the shape of the electrode plateis different from the above-described embodiments. Specifically, in the other embodiment 3, the electrode plateincludes a plurality of slits S and a plurality of through holes H.

40 40 40 The slits S are formed extending, for example, along the width direction (i.e., the direction intersecting the laminate direction D) of the electrode plateto the end surface of either end portion of the electrode plate. The through holes H are formed extending along the same direction as those of the slits S but do not extend to the end surfaces of both the end portions of the electrode plate.

40 The plurality of slits S are alternately cut off from the end surfaces of both the end portions in the width direction of the electrode plateand are arranged at substantially equal intervals along the laminate direction D. The plurality of slits S have substantially equal lengths. Each length of the plurality of slits S is set so that the front end overlaps each other when viewed in the laminate direction D.

40 40 10 40 10 20 In the other embodiment 3, arranging the plurality of slits S in the electrode plateenables the electrode plateto stretch in the laminate direction D, following the stretch of the laminate bodyin the laminate direction D. Therefore, the other embodiment 3 can reduce the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

40 Furthermore, in the other embodiment 3, the through hole H is positioned between the slits S that are alternately cut off from the end surfaces of both the end portions in the width direction at the electrode plate. Such through hole H is arranged at a position that is equally spaced with respect to both adjacent slits S and has a length substantially equal to the length of the slit S.

9 FIG. 40 That is, in the other embodiment 3, as illustrated in, in the electrode plate, the slit S extending from the end surface of one end portion, the through hole H, the slit S extending from the end surface of the other end portion, and the through hole H, are arranged in this order along the laminate direction D at substantially equal intervals.

In the other embodiment 3, the through hole H is arranged at a position where the front end of the slit S extending from one end surface of one end portion and the front end of the slit S extending from the other end surface of the other end portion overlap each other.

40 10 40 10 20 Thus, the stress generated between the slit S extending from one end surface of one end portion and the slit S extending from the other end surface of the other end portion can be dispersed, so that the stress generated in the electrode platedue to the stretch of the laminate bodycan be relaxed. Therefore, the other embodiment 3 can further reduce the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

10 FIG. 10 FIG. 40 is an enlarged plan view illustrating an example of the configuration of the electrode plateaccording to the other embodiment 4. In the other embodiment 4 illustrated in, the arrangement of the through holes H is different from that in the other embodiment 3 described above.

40 Specifically, in the other embodiment 4, in the electrode plate, two or more through holes H are positioned adjacent to each other between the slits S that are alternately cut off from the end surfaces of both the end portions.

10 FIG. 40 For example, as illustrated in, in the electrode plate, the slit S extending from the end surface of one end portion, the through hole H, the through hole H, and the slit S extending from the end surface of the other end portion, are arranged in this order along the laminate direction D at substantially equal intervals.

40 40 10 40 10 20 Thus, by arranging two or more through holes H adjacent to each other between the slits S alternately cut from both end surfaces in the width direction in the electrode plate, the stress generated in the electrode platedue to the stretch of the laminate bodycan be further relaxed. Therefore, the other embodiment 4 can further reduce the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

11 FIG. 12 FIG. 11 FIG. 13 FIG. 11 FIG. 11 13 FIGS.to 40 5 50 is an enlarged plan view illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment.is a cross-sectional view taken along line XII-XII illustrated in.is a cross-sectional view taken along line XIII-XIII illustrated in. In, the illustration of the coating layeris omitted for convenience of description.

11 13 FIGS.to 11 FIG. 40 60 40 10 43 20 30 44 43 43 10 a The other embodiment 5 illustrated indiffers from the above embodiments in the configuration of the electrode plateand in that a fixing materialare newly provided. Specifically, in the other embodiment 5, as illustrated in, the electrode plateis a plate-like member extending in the laminate direction D of the laminate bodyand includes a body portionbonded to the electrical conductor layervia an electrically conductive bonding material, and an extending portionprotruding from one endof the body portionin the laminate direction D and facing the laminate body.

43 431 30 432 431 20 30 The body portionincludes a first portionin contact with the bonding material, and a second portionpositioned on both sides of the first portionin the width direction (i.e., the direction intersecting the laminate direction D) and facing the electrical conductor layerwithout contacting the bonding material.

11 FIG. 43 40 43 As illustrated in, in the other embodiment 5, the body portionof the electrode plateincludes a plurality of slits S. The slits S are cut so as to extend along the width direction (i.e., the direction intersecting the laminate direction D) of the body portion, for example.

432 43 43 The plurality of slits S are alternately cut from both sides (sides of the pair of second portions) of the body portionand are arranged side by side at substantially equal intervals along the laminate direction D. The plurality of slits S have substantially equal lengths. Note that the length of the slit S is the length in the notch direction of the slit S ((i.e., the width direction of the body portion).

Furthermore, each length of the plurality of slits S is set so that the front end overlaps each other when viewed in the laminate direction D. “Overlap” means that the adjacent slits S have areas facing each other when viewed in the laminate direction D.

43 40 43 10 40 10 20 In the other embodiment 5, arranging the plurality of slits S in the body portionof the electrode plateenables the body portionto stretch in the laminate direction D, following the stretch of the laminate bodyin the laminate direction D. Therefore, the other embodiment 5 can reduce the possibility that the electrode plateseparates from the laminate bodyor the electrical conductor layer.

44 40 10 1 The extending portionof the electrode platefaces the laminate bodyacross a first gap G.

1 60 60 40 10 60 44 40 10 The piezoelectric elementaccording to the other embodiment 5 includes the fixing material. The fixing materialfixes the electrode plateand the laminate body. For example, the fixing materialfixes at least the extending portionof the electrode plateto the laminate body.

60 44 10 60 44 10 The fixing materialaccording to the other embodiment 5 may not necessarily fix the entire periphery of the extending portionto the laminate body. That is, the fixing materialmay only fix at least a part of the periphery of the extending portionto the laminate body.

60 44 10 44 44 44 40 The fixing materialaccording to the other embodiment 5 may fix the entire periphery of the extending portionto the laminate bodywhile a predetermined area surrounded by the periphery of the extending portionis left in the extending portion. Thus, the predetermined region left in the extending portioncan be used as a region for connecting the lead terminal for supplying power to the electrode plate.

60 60 60 11 The fixing materialis made of, for example, an insulation material having thermal resistance and flexibility. As the insulation material to be the fixing material, for example, epoxy resin, glass, ceramics, or composite material of epoxy resin and ceramics can be used. When ceramics or composite material of epoxy resin and ceramics are used as the insulation material to be the fixing material, the material of the ceramics may be the same as that of piezoelectric ceramics to be the piezoelectric body.

12 13 FIGS.and 60 44 40 10 44 10 1 60 44 10 1 1 Here, as illustrated in, in the other embodiment 5, the fixing materialfixes at least the extending portionof the electrode plateto the laminate bodywhile the first gap Gis maintained between the extending portionand the laminate body. In other words, in the other embodiment 5, the piezoelectric elementhas the first gap Gbetween the fixing material, the extending portion, and the laminate body.

44 10 43 40 20 60 10 43 40 20 10 40 20 1 a a This causes the extending portionon the first gap Gto stretch in the laminate direction D, following the stretch of the laminate bodyin the laminate direction D. Then, the stress generated at the end portion (near the one end) of the bonding site between the electrode plateand the electrical conductor layercan be released to the interface between the fixing materialand the laminate body. Thus, the other embodiment 5 can disperse the stress generated at the end portion (near the one end) of the bonding site between the electrode plateand the electrical conductor layerdue to the stretch of the laminate bodyin the laminate direction D. This can reduce the possibility that the electrode plateseparates from the electrical conductor layer.

14 15 FIGS.and 14 FIG. 11 FIG. 15 FIG. 11 FIG. 14 15 FIGS.and 40 50 are cross-sectional views illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment 6.corresponds to a cross-sectional view taken along line XII-XII illustrated in, andcorresponds to a cross-sectional view taken along line XIII-XIII illustrated in. In, the illustration of the coating layeris omitted for convenience of description.

14 15 FIGS.and 60 6 60 61 61 44 10 44 44 40 61 In the other embodiment 6 illustrated in, the configuration of the fixing materialis different from that of the other embodiment 5 described above. Specifically, in the other embodiment, the fixing materialhas a protruding portion. The protruding portionis positioned so as to project inward from the periphery of the extending portionand is in contact with the laminate body. Here, “inward from the periphery of the extending portion” can be rephrased as a direction approaching the center axis of the extending portion(electrode plate). The protruding portionis an example of the first protruding portion.

10 43 40 20 61 60 60 10 40 20 10 40 20 a Following the stretch of the laminate bodyin the laminate direction D, a stress is generated at the end portion (near the one end) of the bonding site between the electrode plateand the electrical conductor layer. The other embodiment 6, by providing the protruding portionat the fixing material, can more efficiently release this stress to the interface between the fixing materialand the laminate body. Thus, the other embodiment 6 can more efficiently disperse the stress generated at the end portion of the bonding site between the electrode plateand the electrical conductor layerdue to the stretch of the laminate bodyin the laminate direction D. This can further reduce the possibility that the electrode plateseparates from the electrical conductor layer.

16 FIG. 17 FIG. 16 FIG. 40 is an enlarged plan view illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment 7.is a cross-sectional view taken along line XVII-XVII illustrated in.

16 17 FIGS.and 60 43 20 10 20 43 43 a As illustrated in, the other embodiment 7 fixes, by the fixing material, the body portionand the electrical conductor layerto the laminate bodyat the one end of the electrical conductor layerlocated on the one endside of the body portion.

10 43 40 20 60 10 40 20 10 40 20 a Following the stretch of the laminate bodyin the laminate direction D, a stress is generated at the end portion (near the one end) of the bonding site between the electrode plateand the electrical conductor layer. Thus, the other embodiment 7 can more efficiently release this stress to the interface between the fixing materialand the laminate body. Thus, the other embodiment 7 can more efficiently disperse the stress generated at the end portion of the bonding site between the electrode plateand the electrical conductor layerdue to the stretch of the laminate bodyin the laminate direction D. This can further reduce the possibility that the electrode plateseparates from the electrical conductor layer.

18 FIG. 18 FIG. 16 FIG. 40 is a cross-sectional view illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment 8.corresponds to a cross-sectional view taken along line XVII-XVII illustrated in.

43 431 30 432 431 20 30 432 20 2 As described above, the body portionincludes the first portionin contact with the bonding material, and a second portionpositioned on both sides of the first portionin the width direction (i.e., the direction intersecting a laminate direction D) and facing the electrical conductor layerwithout contacting the bonding material. The second portionfaces the electrical conductor layeracross a second gap G.

18 FIG. 60 60 62 62 432 20 432 44 40 62 In the other embodiment 8 illustrated in, the configuration of the fixing materialis different from that of the other embodiment 7 described above. Specifically, in the other embodiment 8, the fixing materialhas a protruding portion. The protruding portionis positioned so as to project inward from the side of the second portionand contacts the electrical conductor layer. Here, “inward from the side of the second portion” can be rephrased as a direction approaching the center axis of the extending portion(electrode plate). The protruding portionis an example of the second protruding portion.

62 60 60 20 62 60 10 20 10 In the other embodiment 8, by providing the protruding portionat the fixing material, the adhesion force between the fixing materialand the electrical conductor layeris improved compared with when the protruding portionis not provided. Therefore, the adhesion force between the fixing materialand the laminate bodyis improved. Therefore, the other embodiment 8 can reduce the possibility that the electrical conductor layerseparates from the laminate body.

19 FIG. 20 FIG. 19 FIG. 40 is an enlarged plan view illustrating an example of the configuration of the electrode plateand its surroundings according to the other embodiment 9.is a cross-sectional view taken along line XX-XX illustrated in.

19 FIG. 19 FIG. 50 43 20 10 10 10 50 43 20 10 10 10 50 10 10 43 20 a b a b As illustrated in, in the other embodiment 9, the coating layercovering the body portionand the electrical conductor layeris located on the side surface (example of a surface located along the laminate direction D of the laminate body)of the laminate body. Although not illustrated in, the coating layercovering the body portionand the electrical conductor layeris also located on the side surface (example of a surface located along the laminate direction D of the laminate body)of the laminate body. By arranging the coating layeron the side surfacesand, the body portionand the electrical conductor layercan be protected.

50 50 The coating layeris made of, for example, an insulator. For example, fluorine-based resin, silicone resin, epoxy resin, nylon resin, or the like are used as the insulator to be the coating layer.

19 20 FIGS.and 50 60 43 43 a In the other embodiment 9, as illustrated in, the end portion of the coating layercovers the end portion of the fixing materiallocated on the one endside of the body portion.

10 43 40 20 60 10 50 10 40 20 10 40 20 a Following the stretch of the laminate bodyin the laminate direction D, a stress is generated at the end portion (near the one end) of the bonding site between the electrode plateand the electrical conductor layer. Thus, the other embodiment 9 can thus more efficiently release this stress to the interface between the fixing materialand the laminate bodyand the interface between the coating layerand the laminate body. Thus, the other embodiment 9 can more efficiently disperse the stress generated at the end portion of the bonding site between the electrode plateand the electrical conductor layerdue to the stretch of the laminate bodyin the laminate direction D. This can further reduce the possibility that the electrode plateseparates from the electrical conductor layer.

21 FIG. 21 FIG. 19 FIG. 40 10 is a cross-sectional view illustrating an example of the configuration of the electrode plateand its surroundings according to another embodiment.corresponds to a cross-sectional view taken along line XX-XX illustrated in.

21 FIG. 1 FIG. 1 FIG. 50 50 10 10 50 10 10 10 10 10 10 10 a a b c d a b. In the other embodiment 10 illustrated in, the configuration of the coating layeris different from that of the other embodiment 9 described above. Specifically, in the other embodiment 10, the coating layeris positioned on the entire circumference of the side surface including the side surfaceof the laminate body. That is, the coating layeris positioned not only on the side surfacesandof the laminate bodybut also on the side surfaces(see) and(see) that are located between the side surfacesand

10 50 10 10 This allows the other embodimentto disperse the stress generated in the coating layerto the entire periphery of the side surfaces of the laminate body, following the stretch of the laminate bodyin the laminate direction D.

22 FIG. 40 10 10 11 12 10 11 12 is an enlarged plan view illustrating an example of a configuration of the electrode plateand its surroundings according to another embodiment 11. As described above, the laminate bodyis composed of an active sectionA composed by alternately laminating a plurality of piezoelectric bodiesand internal electrodesand an inactive sectionB that is arranged at both ends in the laminate direction D in the active section, includes the piezoelectric bodies, and does not include the internal electrodes.

22 FIG. 40 45 10 44 60 45 10 As illustrated in, in the other embodiment 11, the electrode platehas a large width portionthat is larger in width than other portions at a position overlapping the inactive sectionB in a plan view at least in the extending portion. In the other embodiment 11, the fixing materialmay fix the large width portionto the laminate body.

10 43 40 20 60 10 40 20 10 40 20 a Following the stretch of the laminate bodyin the laminate direction D, a stress is generated at the end portion (near the one end) of the bonding site between the electrode plateand the electrical conductor layer. Thus, the other embodiment 11 can more efficiently release this stress to the interface between the fixing materialand the laminate body. Thus, the other embodiment 11 can more efficiently disperse the stress generated at the end portion of the bonding site between the electrode plateand the electrical conductor layerdue to the stretch of the laminate bodyin the laminate direction D. This can further reduce the possibility that the electrode plateseparates from the electrical conductor layer.

23 FIG. 23 FIG. 19 FIG. 40 is a cross-sectional view illustrating an example of the configuration of the electrode plateand its surroundings according to another embodiment 12.corresponds to a cross-sectional view taken along line XXI-XXI illustrated in.

23 FIG. 44 44 10 44 44 44 44 44 a a In the other embodiment 12 illustrated in, the extending portionis inclined such that the distance between the extending portionand the laminate bodybecomes narrow toward a front endof the extending portion. In other words, the extending portionis inclined downward toward the front endof the extending portion.

60 44 44 10 60 44 44 10 a a As a result, in the other embodiment 12, a part of the fixing materialin the uncured state is appropriately filled in the gap between the front endof the extending portionand the laminate body, so that the adhesion strength, after the fixing materialis cured, between the front endof the extending portionand the laminate body, can be improved.

9 10 FIGS.and 40 In, the shape of the through hole H is rectangular in a plan view but may be rounded near the end portion in the width direction of the electrode plate. At this time, the possibility can be reduced that the stress concentrates on the corner portion and cracks are generated during the stretch.

1 11 3 3 A method of manufacturing an example of the piezoelectric elementaccording to the present embodiment will be described. A ceramic green sheet to be a piezoelectric body layer (piezoelectric body) is produced. Specifically, a ceramic slurry is produced by mixing calcined powder of piezoelectric ceramics, a binder having an organic polymer such as acrylic or butyral, and a plasticizer. A ceramic green sheet is produced from the ceramic slurry by using a tape molding method such as a well-known doctor blade method and a calender roll method. As the piezoelectric ceramics, any material having piezoelectric properties may be used. For example, a perovskite oxide having Pb ZrO—PbTiO, or the like can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

12 10 An electrically conductive paste as the internal electrodeis produced. Specifically, an electrically conductive paste is produced by adding and mixing a binder and a plasticizer to metal powder of silver-palladium alloy. The electrically conductive paste is printed on the ceramic green sheet by screen printing. A plurality of ceramic green sheets printed with the electrically conductive paste are stacked, and a plurality of ceramic green sheets not printed with the electrically conductive paste are stacked on both ends in the laminate direction to obtain a multilayer molded body. The laminate molded body is subjected to debinding treatment at a predetermined temperature and is then baked at 900 to 1200° C. to obtain the laminate body.

10 20 10 20 Subsequently, the electrically conductive paste consisting of silver and glass is coated on the side surface of the laminate bodyand is baked to form the electrical conductor layer. The electrically conductive paste is made by adding and mixing a binder, plasticizer, glass powder, or the like to a metal powder consisting mainly of silver. Printing the electrically conductive paste on the side surface of the laminate bodyby screen printing or the like and baking it at 600 to 800° C. can form the electrical conductor layer.

30 20 40 30 40 The bonding materialis applied to the upper surface of the electrical conductor layer, and an electrode plateis stuck thereon, and then the bonding materialis dried at a temperature of 100 to 140° C. and is then cured at a temperature of 180 to 220° C. to fix the electrode plate.

50 10 50 50 50 Then, the coating layeris coated on the laminate bodyby a general coating method such as dipping, defoaming treatment is performed, and the coating layeris then cured. This may cause microscopic void of 0.1 μm or less to be dispersed in the coating layerbut forms no gap G. Then, the gap G can also be formed by using a resin with high viscosity as the coating layerand applying the resin to a predetermined position by screen printing. Note that for example, the gap G can also be formed by the following method as another method.

50 10 40 20 50 1 The photosensitive coating layeris applied to the laminate body. Then, the gap G is provided between the electrode plateand the electrical conductor layer, and the gap G is irradiated with light and cured before the coating layerflows into the gap G. The piezoelectric elementof the present example is produced by the above method.

50 50 30 40 20 40 30 40 50 40 A method of applying the coating layertwice may also be used. Specifically, the coating layeris applied before the bonding materialand the electrode plateare fixed. Then, after exposing the electrical conductor layerby plasma etching or blast treatment to the place where the electrode plateis to be fixed, the bonding materialand the electrode plateare fixed, and the coating layeris applied again on the electrode plateto form the gap G.

40 41 42 10 41 42 20 50 50 41 42 50 1 7 8 FIGS.and The electrode platehaving the projecting portion() described inis fixed to the laminate bodyto reduce the distance between the projecting portion() and the electrical conductor layer, and the coating layeris applied by screen printing. This causes the coating layerto less likely to flow into the projecting portion(), and in this state, the coating layeris hardened to form the gap G. The piezoelectric elementof the present example is produced by the above method.

1 10 20 40 50 11 12 30 As described above, the piezoelectric element (e.g., piezoelectric element) according to the embodiments includes the laminate body (e.g., laminate body), the electrical conductor layer (e.g., electrical conductor layer), the electrode plate (e.g., electrode plate), and the coating layer (e.g., coating layer). The laminate body includes a plurality of the piezoelectric bodies (e.g., piezoelectric body) and a plurality of internal electrodes (e.g., internal electrode) laminated. The electrical conductor layer is connected to the internal electrodes and is positioned along the laminate direction (e.g., laminate direction D) of the laminate body. The electrode plate is bonded to the electrical conductor layer via the electrically conductive bonding material (e.g., bonding material) and is positioned along the laminate direction of the laminate body. The coating layer covers the electrical conductor layer and the electrode plate. The electrode plate includes a plurality of slits (e.g., slit S) extending in the direction (e.g., width direction) intersecting the laminate direction. The piezoelectric element has a first gap (e.g., the gap G) between the electrode plate, the electrical conductor layer, and the bonding material. This can reduce the possibility of separation of the electrode plate covered with the coating layer.

Note that with respect to the above embodiments, the following additional notes are disclosed.

a laminate body with a plurality of piezoelectric bodies and a plurality of internal electrodes laminated; an electrical conductor layer connected to the plurality of internal electrodes and positioned along a laminate direction of the laminate body; an electrode plate bonded to the electrical conductor layer via a bonding material having electrical conductivity and positioned along the laminate direction of the laminate body; and a coating layer covering the electrical conductor layer and the electrode plate, wherein the electrode plate includes a plurality of slits extending in a direction intersecting the laminate direction, and the piezoelectric element includes a first gap between the electrode plate, the electrical conductor layer, and the bonding material. A piezoelectric element, including:

The piezoelectric element according to Supplementary Note 1, wherein the coating layer includes a first protruding portion protruding inward from an end portion of the electrode plate in the direction intersecting the laminate direction and contacting the electrical conductor layer.

The piezoelectric element according to Supplementary Note 1 or 2, wherein the electrode plate includes a first projecting portion projecting in a thickness direction of the electrode plate at a periphery of an end portion of the electrode plate in the direction intersecting the laminate direction.

The piezoelectric element according to Supplementary Note 3, wherein the first projecting portion extends along the laminate direction of the laminate body.

The piezoelectric element according to any one of Supplementary Notes 1 to 4, wherein the coating layer includes a second protruding portion protruding inward from inner wall surfaces of the slits in the electrode plate and contacting the electrical conductor layer.

The piezoelectric element according to any one of Supplementary Notes 1 to 5, wherein the electrode plate includes a second projecting portion projecting in a thickness direction of the electrode plate at the periphery of the slits.

The piezoelectric element according to Supplementary Note 6, wherein the second projecting portion extends along a longitudinal direction of the slits.

The piezoelectric element according to any one of Supplementary Notes 1 to 7, wherein a gap between one end portion of the electrode plate positioned outside from the bonding material in a width direction of the electrode plate in a plan view and the electrical conductor layer is separated from a gap between the other end portion of the electrode plate and the electrical conductor layer.

The piezoelectric element according to any one of Supplementary Notes 1 to 8, wherein the electrode plate includes a through hole positioned between the slits adjacent to each other.

Further effects and other embodiments can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments represented and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.